updated 4/26/2005 2:10:34 PM ET 2005-04-26T18:10:34

For years, both consumers and researchers have tried to decide whether it’s better to eat three meals a day or graze throughout the day, consuming small amounts of food. Do the “mini-meals” of grazing speed up metabolism and make weight control easier, or does spreading out food intake make people eat more and gain weight? What effect does grazing have on blood sugar and cholesterol?

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A new study tried to answer these questions. In it, 10 obese but otherwise healthy women ate their usual amount of food in three regular meals per day for two weeks. For another two weeks, the women varied the number of times a day they ate from three to nine times, but they still tried to eat the same total amount of food.

Food diaries of the women in this study showed that they ate fewer total calories on the days with three regular meals. Although the women’s weight was unaffected by the irregular eating patterns, weight gain wouldn’t be expected after only two weeks of eating 80 calories a day more by grazing. However, the impact of eating frequency on calorie intake remains unclear. When a group of lean women went through the same tests of three regular meals versus irregular eating in a separate study, there was no difference in calorie intake.

Effect on metabolic rate unclear
Grazing is often said to lead to a higher calorie-burning rate. In this study, however, the women’s baseline metabolic rate, which is how fast the body burns calories, was unaffected by differences in meal timing. Contrary to popular thought, other studies also show that eating frequency has no effect on a person’s overall metabolic rate.

Another aspect of metabolism, however, did change. The rate of calorie-burning immediately after eating, which naturally rises as the body processes food, rose considerably higher after two weeks of eating just three meals a day. Both the obese and lean women experienced this increase in metabolism. In other studies, however, the effect of meal frequency on the metabolic rate after meals varied.

What about cholesterol?
People might think that grazing would improve blood cholesterol or blood sugar control because the body processes smaller amounts of food at a time. But results are mixed. In this recent study, LDL (“bad”) cholesterol was actually higher after two weeks of irregular eating. However, some past studies have shown lower LDL levels with grazing.

The effect of meal frequency on blood sugar also varies in studies. In the recent study of obese and lean women, pre-breakfast insulin levels were unaffected by either meal pattern, but insulin levels rose less after eating with three meals a day. The irregular eating pattern led to increased insulin levels and apparently less effective insulin action. In another study, when people ate identical foods in either three meals or nine snacks, the snacking pattern was linked to higher fasting blood sugar levels but lower insulin levels, which is a mixed bag of results. In general, however, neither meal nor grazing patterns seem to have a health advantage when compared to each other.

Perhaps the biggest impact of a person’s eating style depends on what is eaten. For some people, spreading out food intake means smaller portions of a variety of healthy foods. Other people, however, may select less balanced food choices when grazing. Some studies show that regular meals, on the other hand, result in a greater consumption of vegetables, fruits and whole grains, along with a higher intake of protein, calcium, fiber and a variety of vitamins.

If grazing for you means more high-calorie food, or fewer vegetables and whole grains, then you need to change your food choices for a healthier grazing habit. If you want to control your weight, you need to decide whether grazing makes you more likely to overeat.

Nutrition Notes is provided by the American Institute for Cancer Research in Washington, D.C.

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